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use nom::{
branch::alt,
character::complete::{char, line_ending},
combinator::{map, value},
multi::{many1, separated_list1},
IResult,
};
use std::fs;
fn main() -> Result<(), Box<dyn std::error::Error>> {
let input = fs::read_to_string("inputs/day_11.txt")?;
let galaxy_map = GalaxyMap::parser(&input).unwrap().1;
let part_1_expanded_galaxy_map = galaxy_map.expand(2);
dbg!(&part_1_expanded_galaxy_map.distance_sum_between_galaxies());
let part_2_expanded_galaxy_map = galaxy_map.expand(1_000_000);
dbg!(&part_2_expanded_galaxy_map.distance_sum_between_galaxies());
Ok(())
}
#[derive(Debug)]
struct GalaxyMap(Vec<Point>);
#[derive(Debug, Clone)]
struct Point {
x: usize,
y: usize,
}
#[derive(Debug, Clone)]
enum Token {
Space,
Galaxy,
}
impl GalaxyMap {
fn parser(input: &str) -> IResult<&str, Self> {
map(
separated_list1(
line_ending,
many1(alt((
value(Token::Space, char('.')),
value(Token::Galaxy, char('#')),
))),
),
|rows| {
GalaxyMap(
rows.into_iter()
.enumerate()
.flat_map(move |(y, row)| {
row.into_iter()
.enumerate()
.filter_map(move |(x, token)| match token {
Token::Space => None,
Token::Galaxy => Some(Point { x, y }),
})
})
.collect(),
)
},
)(input)
}
fn expand(&self, expansion_factor: usize) -> GalaxyMap {
let max_y = self.0.iter().map(|p| p.y).max().unwrap();
let empty_rows: Vec<usize> = (0..max_y)
.filter(|y| !self.0.iter().any(|p| p.y == *y))
.collect();
let max_x = self.0.iter().map(|p| p.x).max().unwrap();
let empty_cols: Vec<usize> = (0..max_x)
.filter(|x| !self.0.iter().any(|p| p.x == *x))
.collect();
let extra_spaces = expansion_factor - 1;
GalaxyMap(
self.0
.iter()
.map(|p| Point {
x: p.x
+ empty_cols.iter().filter(|empty_x| **empty_x < p.x).count()
* extra_spaces,
y: p.y
+ empty_rows.iter().filter(|empty_y| **empty_y < p.y).count()
* extra_spaces,
})
.collect(),
)
}
fn distance_sum_between_galaxies(&self) -> usize {
let mut sum = 0;
for i in 0..self.0.len() {
for j in i + 1..self.0.len() {
sum += self.0[i].distance_to(&self.0[j]);
}
}
sum
}
}
impl Point {
fn distance_to(&self, other: &Point) -> usize {
other.x.abs_diff(self.x) + other.y.abs_diff(self.y)
}
}
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